The present invention relates to a defect inspection method and inspection device used to inspect microscopic defects present on a specimen surface and determine, output the kinds and sizes of defects.
At manufacturing lines for semiconductor substrates or thin-film substrates or the like, defects on the surface of a semiconductor substrate or thin-film substrate or the like are inspected to maintain/improve product yields. Known conventional techniques relating to defect inspection include those disclosed in, for example, Japanese Patent Application Publications JP-A-1997-304289 (Patent Document 1), JP-A-2006-201179 (Patent Document 2), and US Patent Application No. 2006/0256325 (Patent Document 3). In these conventional techniques, in order to detect microscopic defects, the surface of a specimen is irradiated with illumination light focused to a size of tens of micrometers (μm). The scattered light from each defect is focused and detected, thereby inspecting defects with a size measuring between tens of nanometers (nm) and tens of micrometers (μm) or larger. A stage holding the specimen (target substance) can be moved rotationally and translationally to helically scan the surface of the specimen and inspect the entire surface of the specimen.
Patent Documents 1 and 2 also describe techniques that detect high-angle emission components and low-angle emission components of the scattered light from defects to classify the defects based on the ratio between the two.
Patent Document 2 also describes a technique for calculating dimensions of a detected defect based on the intensity of the scattered light from the defect.
Patent Document 3 also describes a technique, for reducing thermal damage to the specimen, that controls power of illumination light, a scanning speed of the illumination spot, or a size of the illumination spot during the inspection of the intended surface. More specifically, the technique assumes that the thermal damage to the specimen is determined by a product of a density and irradiation time of the irradiating illumination power. In order to keep the product lower than a fixed value, the power of the illumination light, the scanning speed of the illumination spot, or the size of the illumination spot is changed in accordance with the radial position on the specimen under scanning.
In addition, U.S. Pat. No. 6,608,676 (Patent Document 4) discloses a technique for inspecting an entire surface of a specimen within a short time. A unidirectionally long gaussian beam is used to illuminate a broad region of the specimen and the entire illuminated region is detected at one time by a multi-pixel detector such as a CCD.
Furthermore, U.S. Pat. No. 7,385,688 (Patent Document 5) discloses a technique that uses a non-spherical lens or a diffractive optical element in off-axis illumination so that illumination light is shaped into an array of illumination spots on the surface of a target object.